Demand for high quality multimedia data over the Internet in themobile environment has been growing rapidly. Popularity of video streaminghas greatly increased recently and real-time entertainment data including videoand audio now accounts for a majority of Internet traffic. Video conferencingis also gaining popularity and is becoming accessible to non-enterprise users.With the advent of mobile Internet such multimedia applications are nowbecoming more popular in the mobile environment, however efficient contentdelivery in such cases yet remains a challenging problem.

The mobile environment is significantly more unfriendly than the wiredenvironment in many ways for multimedia applications. Network resources aremore limited and expensive and the condition is not as stable which makesprediction difficult. However multimedia applications are generally delay intol-erant and bandwidth demanding, and with users moving their demand could bemuch more dynamic and harder to anticipate. Due to such reasons many exist-ing mobile applications for multimedia services such as multimedia streamingor video conferencing are not well optimized for mobile environment and showunsatisfactory performance.

We target three multimedia content delivery applications and optimizewith limited and unpredictable network conditions typical in the mobile Inter-net environment.

Vehicular Networks: Vehicular networks have emerged from the strongdesire to communicate on the move. We explore the potential of supportinghigh-bandwidth applications such as video streaming in vehicular networks.Challenges include limited and expensive cellular network, etc.

Video Conferencing: The popularity of Internet video conferencing hassurged over the past few years, but supporting high-quality large video confer-ences at a low cost remains a significant challenge due to stringent performancerequirements, limited and heterogeneous client. We develop a simple yet ef-fective valiant multicast routing to select application-layer routes and adaptstreaming rates according to dynamically changing network condition in aswift and lightweight way enough to be implemented on mobile devices.

Mobile Video Streaming and Rate Adaptation : We target the rate ada-pative online video streaming application and are developing a real system thatimplements a novel rate selection strategy that can maximize user-perceivedvideo quality. The system aims to minimize rate changes while maximizingaverage video streaming rate by dynamically adapting to changing networkconditions. This is an onoing work and we plan to further extend the idea tooptimize aggregated user-perceived streaming quality of clients that share thesame network bottleneck through inter-client optimization.